Schneider CPC 6128 mainboard problem

[SzoorG]

Greetings to all! :-)


Thanks to the inclusion in the forum! I'm happy to be here :-)
I am a retro computer collector from Hungary.


I bought a injured Schneider CPC6128 with a working CTM644 color monitor.


The motherboard will not start, it shows often a gray screen, by multiple power up
shows a color charts (see pictures).
I tried with another monitor (Amstrad GT65), it is a same result. The Z80 CPU and
Amstrad 40010 ICs operate fine with another machine (CPC 464).

I found at the ROM IC's some corrosion by VIA, but I was fixed it.
I measured, there is no more break in the lines. :-)


Does anyone have suggestions to repair?

[Bryce]

Hi and welcome SzoorG,
      One of your Lower (first 64K) RAM ICs has failed.

Bryce.

[||C|-|E||]

I knew it! 

Sorry, I am writing this because when I saw the pictures I thought "I am sure that it is the RAM" but I did not dare to say anything and I was waiting for your expert opinion 

[Bryce]

RAM is always an obvious one. The fact that it got to a border means that nearly everything else has been proven to work.

Bryce.

[SzoorG]

RAM is always an obvious one. The fact that it got to a border means that nearly everything else has been proven to work.

Bryce.

Thans for quick answer ! :-) I have two tips, RAM IC failure / ROM failure.



If the ram IC warms up, it's probably wrong?

[TFM]

Right! I would go for new RAM chip(s) too.


Good luck!    And welcome to the forum. 

[Bryce]

I've been fixing CPCs for years and I've never come across a failed ROM unless it was "helped".

Bryce.

Gesendet von meinem Motorola DynaTEC 8000X mit Tapatalk 2.

[SzoorG]

Thanks for infos :-)
I'm trying repair ...

[Bryce]

There's a trick to swap banks so that the upper 64K become the lower 64K and the CPC should then boot properly. This would confirm that the RAM is the problem. Can't remember exactly where this info is, but it was mentioned here lately in a different thread.

Bryce.